Note: for server version, if there are more than 4 processors, the initial_segment_size is cut in half.

So with 2.0 framework on 4 Processor machine on x64 bit OS

Initial virtualalloc() == 4 * (1GB + 256MB) = 5GB

Now since you have a x64, 4 proc box, it means that you are going to use somewhere above 5 GB of reserved address space.

This is because we want to reduce the overhead of GC triggering again and again considering the fact that we have 16 terrabytes of virtual memory

On a 64-bit environment as the total virtual memory limit is practically limitless[16 terabytes(8 usermode TB + 8 kernel TB)].

Thinking of Virtual Memory as a constraint applies to the 32-bit world since we have a limit of 2GB (or 3GB with /3gb switch in c:/boot.ini),which is pretty low

The memory that needs to be monitored and should of concern is the working set[Direct on RAM]/private bytes[committed size], as that would be constrained by the amount of physical memory on the servers.